1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
|
;; Copyright (C) 2001, 2004 Free Software Foundation, Inc.
;;
;; This file is part of GCC.
;;
;; GCC is free software; you can redistribute it and/or modify it under
;; the terms of the GNU General Public License as published by the Free
;; Software Foundation; either version 3, or (at your option) any later
;; version.
;;
;; GCC is distributed in the hope that it will be useful, but WITHOUT ANY
;; WARRANTY; without even the implied warranty of MERCHANTABILITY or
;; FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
;; for more details.
;;
;; Under Section 7 of GPL version 3, you are granted additional
;; permissions described in the GCC Runtime Library Exception, version
;; 3.1, as published by the Free Software Foundation.
;;
;; You should have received a copy of the GNU General Public License and
;; a copy of the GCC Runtime Library Exception along with this program;
;; see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
;; <http://www.gnu.org/licenses/>.
;;
;; This code used to be expanded through interesting expansions in
;; the machine description, compiled from this code:
;;
;; #ifdef L_mulsi3
;; long __Mul (unsigned long a, unsigned long b) __attribute__ ((__const__));
;;
;; /* This must be compiled with the -mexpand-mul flag, to synthesize the
;; multiplication from the mstep instructions. The check for
;; smaller-size multiplication pays off in the order of .5-10%;
;; estimated median 1%, depending on application.
;; FIXME: It can be further optimized if we go to assembler code, as
;; gcc 2.7.2 adds a few unnecessary instructions and does not put the
;; basic blocks in optimal order. */
;; long
;; __Mul (unsigned long a, unsigned long b)
;; {
;; #if defined (__CRIS_arch_version) && __CRIS_arch_version >= 10
;; /* In case other code is compiled without -march=v10, they will
;; contain calls to __Mul, regardless of flags at link-time. The
;; "else"-code below will work, but is unnecessarily slow. This
;; sometimes cuts a few minutes off from simulation time by just
;; returning a "mulu.d". */
;; return a * b;
;; #else
;; unsigned long min;
;;
;; /* Get minimum via the bound insn. */
;; min = a < b ? a : b;
;;
;; /* Can we omit computation of the high part? */
;; if (min > 65535)
;; /* No. Perform full multiplication. */
;; return a * b;
;; else
;; {
;; /* Check if both operands are within 16 bits. */
;; unsigned long max;
;;
;; /* Get maximum, by knowing the minimum.
;; This will partition a and b into max and min.
;; This is not currently something GCC understands,
;; so do this trick by asm. */
;; __asm__ ("xor %1,%0\n\txor %2,%0"
;; : "=r" (max)
;; : "r" (b), "r" (a), "0" (min));
;;
;; if (max > 65535)
;; /* Make GCC understand that only the low part of "min" will be
;; used. */
;; return max * (unsigned short) min;
;; else
;; /* Only the low parts of both operands are necessary. */
;; return ((unsigned short) max) * (unsigned short) min;
;; }
;; #endif /* not __CRIS_arch_version >= 10 */
;; }
;; #endif /* L_mulsi3 */
;;
;; That approach was abandoned since the caveats outweighted the
;; benefits. The expand-multiplication machinery is also removed, so you
;; can't do this anymore.
;;
;; For doubters of there being any benefits, some where: insensitivity to:
;; - ABI changes (mostly for experimentation)
;; - assembler syntax differences (mostly debug format).
;; - insn scheduling issues.
;; Most ABI experiments will presumably happen with arches with mul insns,
;; so that argument doesn't really hold anymore, and it's unlikely there
;; being new arch variants needing insn scheduling and not having mul
;; insns.
;; ELF and a.out have different syntax for local labels: the "wrong"
;; one may not be omitted from the object.
#undef L
#ifdef __AOUT__
# define L(x) x
#else
# define L(x) .x
#endif
.global ___Mul
.type ___Mul,@function
___Mul:
#if defined (__CRIS_arch_version) && __CRIS_arch_version >= 10
;; Can't have the mulu.d last on a cache-line (in the delay-slot of the
;; "ret"), due to hardware bug. See documentation for -mmul-bug-workaround.
;; Not worthwhile to conditionalize here.
.p2alignw 2,0x050f
mulu.d $r11,$r10
ret
nop
#else
move.d $r10,$r12
move.d $r11,$r9
bound.d $r12,$r9
cmpu.w 65535,$r9
bls L(L3)
move.d $r12,$r13
movu.w $r11,$r9
lslq 16,$r13
mstep $r9,$r13
mstep $r9,$r13
mstep $r9,$r13
mstep $r9,$r13
mstep $r9,$r13
mstep $r9,$r13
mstep $r9,$r13
mstep $r9,$r13
mstep $r9,$r13
mstep $r9,$r13
mstep $r9,$r13
mstep $r9,$r13
mstep $r9,$r13
mstep $r9,$r13
mstep $r9,$r13
mstep $r9,$r13
clear.w $r10
test.d $r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
movu.w $r12,$r12
move.d $r11,$r9
clear.w $r9
test.d $r9
mstep $r12,$r9
mstep $r12,$r9
mstep $r12,$r9
mstep $r12,$r9
mstep $r12,$r9
mstep $r12,$r9
mstep $r12,$r9
mstep $r12,$r9
mstep $r12,$r9
mstep $r12,$r9
mstep $r12,$r9
mstep $r12,$r9
mstep $r12,$r9
mstep $r12,$r9
mstep $r12,$r9
mstep $r12,$r9
add.w $r9,$r10
lslq 16,$r10
ret
add.d $r13,$r10
L(L3):
move.d $r9,$r10
xor $r11,$r10
xor $r12,$r10
cmpu.w 65535,$r10
bls L(L5)
movu.w $r9,$r13
movu.w $r13,$r13
move.d $r10,$r9
lslq 16,$r9
mstep $r13,$r9
mstep $r13,$r9
mstep $r13,$r9
mstep $r13,$r9
mstep $r13,$r9
mstep $r13,$r9
mstep $r13,$r9
mstep $r13,$r9
mstep $r13,$r9
mstep $r13,$r9
mstep $r13,$r9
mstep $r13,$r9
mstep $r13,$r9
mstep $r13,$r9
mstep $r13,$r9
mstep $r13,$r9
clear.w $r10
test.d $r10
mstep $r13,$r10
mstep $r13,$r10
mstep $r13,$r10
mstep $r13,$r10
mstep $r13,$r10
mstep $r13,$r10
mstep $r13,$r10
mstep $r13,$r10
mstep $r13,$r10
mstep $r13,$r10
mstep $r13,$r10
mstep $r13,$r10
mstep $r13,$r10
mstep $r13,$r10
mstep $r13,$r10
mstep $r13,$r10
lslq 16,$r10
ret
add.d $r9,$r10
L(L5):
movu.w $r9,$r9
lslq 16,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
mstep $r9,$r10
ret
mstep $r9,$r10
#endif
L(Lfe1):
.size ___Mul,L(Lfe1)-___Mul
|
